Challenging My Auto Loan

I am interested in challenging my auto loan...How should I go about this? Can someone point me in the right direction?

Now my questions are, what happens to my car if I am successful with this?

What does this all mean for credit ratings and SSN's?

I operate a small eBay business and my Payment processor requires SSN for tax purposes...If I oppt in, does this mean I can no longer do business with anything that is part of the system?

Sorry if these are dumb questions lol I am new to this and still trying to fully wrap my head around it.